A typical automotive steering wheel has an inner frame formed of metal, the frame having a central portion or boss to be connected to a steering column and a plurality of spokes which extend radially outwardly from the boss to a peripheral rim. Typically the rim makes a full circle.
The frame is provided with a covering, which, in a prior proposed steering wheel, may comprise an inner core formed of polyurethane foam and an outer covering or skin formed of a plastics material such as a thermoplastic material. The polyurethane foam is light, but is a toxic material and, with present day technology, cannot be recycled.
A steering wheel must have specific dimensions, and the rim part of a steering wheel must have a dimension suitable for it to be readily grasped by hand.
The present invention seeks to provide an improved steering wheel in which polyurethane foam is not utilised but in which the weight of the steering wheel is maintained within an acceptable range.
According to a first aspect of the present invention, there is provided a steering wheel for a motor vehicle, the steering wheel having a metal frame, the metal frame defining a boss portion to be connected to a steering column, at least one spoke and a peripheral rim, at least the peripheral rim being provided with a surrounding integral plastics moulding, there being at least one cavity within the integral plastics moulding.
According to another aspect of this invention there is provided a steering wheel for a motor vehicle, the steering wheel having a metal frame, the metal frame defining a boss portion to be connected to a steering column, at least one spoke and a peripheral rim, at least the peripheral rim being provided with a surrounding integral plastics moulding, wherein there is a single closed cavity within the integral plastics moulding, the walls of the cavity being defined by the plastic moulding.
Advantageously, the rim of the frame is located at a position within the surrounding moulding which, when viewed in section, is such that the metal rim of the frame is off-set from the centre of the moulding.
Conveniently, the rim of the frame is provided with two orthogonal arms, the centre of gravity of the rim of the frame at any point being adjacent the centre of the moulding provided on the rim of the frame.
According to a further aspect of this invention there is provided a steering wheel for a motor vehicle, the steering wheel having a metal frame, the metal frame defining a boss portion to be connected to a steering column, at least one spoke and a peripheral rim, at least the peripheral rim being provided with a surrounding integral plastics moulding, wherein there is at least one cavity within the integral plastics moulding, and the peripheral rim includes a pair of orthogonal arms and is located at a position within the surrounding moulding which, when viewed in section, is off-set from the centre of the moulding.
Preferably, at least part of the moulding surrounding the rim is provided with a flexible over-moulding. Alternatively at least part of the rim is provided with a wood or leather outer sleeve.
According to another aspect of the present invention there is provided a method of making a steering wheel, the method comprising the steps of: preparing a mould defining a cavity to receive a frame for a steering wheel, the frame having a portion defining a boss to be secured to a steering column, at least one spoke and a rim connected to the spoke; the mould defining a mould cavity surrounding at least the rim, the mould cavity being provided with an injector arrangement to inject a molten plastics material and a propellant into part of the mould chamber to receive the rim of the steering wheel, the method further comprising the steps of: locating the mould in a force field, injecting plastics material into the mould at such a position, relative to the force field, that a predetermined part of the mould becomes filled with the plastics material; allowing the plastics material in contact with the surface of the mould to at least partially solidify; injecting a propellant into the mould cavity so that still molten plastics material spaced from the walls of the mould is driven into parts of the mould further from the injector arrangement; and permitting the thus driven plastics material to solidify on the walls of the mould, thus producing a steering wheel having an integral moulding surrounding the rim of the frame, with that integral moulding incorporating a chamber or cavity.
Preferably, the propellant is air. Alternatively, the propellant is another gas. In another alternative embodiment, the propellant is water.
Preferably, the injector arrangement is withdrawn from the cavity within the integral moulding and the cavity is sealed.